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Patient-specific Alzheimer-like pathology in trisomy 21 cerebral organoids reveals BACE2 as a gene dose-sensitive AD suppressor in human brain

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posted on 28.01.2022, 10:22 by Ivan Alić, Pollyanna A Goh, Aoife Murray, Erik Portelius, Eleni Gkanatsiou, Gillian Gough, Kin Y Mok, David Koschut, Reinhard Brunmeir, Yee Jie Yeap, Niamh L O’Brien, Jürgen Groet, Xiaowei Shao, Steven Havlicek, N Ray Dunn, Hlin Kvartsberg, Gunnar Brinkmalm, Rosalyn Hithersay, Carla Startin, Sarah Hamburg, Margaret Phillips, Konstantin Pervushin, Mark Turmaine, David Wallon, Anne Rovelet-Lecrux, Hilkka Soininen, Emanuela Volpi, Joanne E Martin, Jia Nee Foo, David L Becker, Agueda Rostagno, Jorge Ghiso, Željka Krsnik, Goran Šimić, Ivica Kostović, Dinko Mitrečić, LonDownS Consortium, Paul T Francis, Kaj Blennow, Andre Strydom, John Hardy, Henrik Zetterberg, Dean Nižetić
A population of more than six million people worldwide at high risk of Alzheimer’s disease (AD) are those with Down Syndrome (DS, caused by trisomy 21 (T21)), 70% of whom develop dementia during lifetime, caused by an extra copy of β-amyloid-(Aβ)-precursor-protein gene. We report AD-like pathology in cerebral organoids grown in vitro from non-invasively sampled strands of hair from 71% of DS donors. The pathology consisted of extracellular diffuse and fibrillar Aβ deposits, hyperphosphorylated/pathologically conformed Tau, and premature neuronal loss. Presence/absence of AD-like pathology was donor-specific (reproducible between individual organoids/iPSC lines/experiments). Pathology could be triggered in pathology-negative T21 organoids by CRISPR/Cas9-mediated elimination of the third copy of chromosome 21 gene BACE2, but prevented by combined chemical β and γ-secretase inhibition. We found that T21 organoids secrete increased proportions of Aβ-preventing (Aβ1–19) and Aβ-degradation products (Aβ1–20 and Aβ1–34). We show these profiles mirror in cerebrospinal fluid of people with DS. We demonstrate that this protective mechanism is mediated by BACE2-trisomy and cross-inhibited by clinically trialled BACE1 inhibitors. Combined, our data prove the physiological role of BACE2 as a dose-sensitive AD-suppressor gene, potentially explaining the dementia delay in ~30% of people with DS. We also show that DS cerebral organoids could be explored as pre-morbid AD-risk population detector and a system for hypothesis-free drug screens as well as identification of natural suppressor genes for neurodegenerative diseases.

Funding

Crick (Grant ID: 10194, Grant title: Tybulewicz FC001194)

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